You have a big future in trouble shooting these gas valves! Part 2 is the pressurized air into the manifold and part 3 is the voltage signals going into the valve. You are a very smart technician! Keep up this good work!
Thank you for your great video teaching how to troubleshoot the gas valve. My gas company just installed the new gas meter at my house. I turned on the gas furnace, but it was not working. I saw the hot surface ignitor glowed, and I heard the relay click sound from the gas valve, but I did not see any flame, and did not hear any hissing sound of the gas flow from the manifold. Now I am not sure if the failure is due to the fact that there is no gas fed to the inlet of the gas valve, or due to a bad gas valve. I would like to check the gas supply first. Could you please advise what would be a proper and easy way to check if the gas is present at the inlet of the gas valve? I know the best way is to use a manometer to measure the gas pressure at the inlet port, but unfortunately I do not have one right now. I ordered one and should arrive in a week or so, but if there is a easy way without using a manometer, I would like to try it now. Thank you!
So, I'm not a plumber so I wouldn't be able to talk about the nuances of wc pressure (gas pressure) but I can say, if you hear the click from the solenoid on the gas valve but it isn't lighting it could be power related, (board isn't sending constant 24v) or gas pressure issues, or bad gas valve. Other things to note, there could be a clog in your burner plates on the burner trail, or the brass orifices coming off of the manifold could also be clogged.
Sorry for the super late response, I'm sure you've found the answer by now but just in case I can give some insight. When the solenoid on the gas valve is stuck open, there's one of two things happening here: Either the gas valve is receiving signal from the control board to come on, or the solenoid is bad. An easy test for that is to remove the two wires from your gas valve, connect your leads to each one and then turn on the unit. (always make sure the door switch is taped in before calling for heat.) Just as your ignitor starts to come on, you should get your 26-28 volts ac until the unit will fault out for no flame sensed. If the valve is at fault and staying stuck open, that is a new gas valve. As far as leaking, if you are concerned about that (which uh, yeah you should be), turn your shut-off valve on your gas line by the unit to off. That's common sense, but figured I'd add that in for good measure.
Very informative video. One question about the voltage test: I saw a reading of 14 VAC before the board sends 24 vac to the gas valve. Is the reading supposed to be zero, other than 14 vac? On my own Bryant gas furnace, I noticed the same 14 Vac reading.
It can really depend on the type of gas valve and unit you have. I've seen units that send a sort of 'test' voltage to make sure the ignitor is coming on like it should (I think Trane and some carrier have a smart sense ignitor) and some boards that also send a blip to see if the gas valve is there. Basically not enough to turn it on. Usually, however, I see this on smart valves which manufacturer's stopped using because of all the issues they kept having.
Nobody knows what is wrong with my furnace. It runs great but when it gets warm in the afternoon and doesn't run for a couple hours it won't restart until I do a hard reset. Then it works perfectly all night long. I've had multiple people out here. One guy wanted to replace the valve but it runs perfectly after hard reset all night. It's a newer furnace. Coleman DGAX090BDTA. It hasn't been cleaned for awhile. My dad did it but he passed and I just didn't get it done. The filter is a month old and is a 3 month filter. The code is 1 red flashing. Please help me. Thank you.
I have a Rheem criterion 2 furnace. It’s started to only blow warm air, not hot like usual. What could be causing this? It starts up like normal, seems to run normally, but only puts out warm air. I’ve tried by passing the high limit switch and thermostat. Same result.
Or folks. You could just have an HVAC technician come out with the proper tools such as a manometer to verify that the gas valve has the proper gas pressure as well as allowing gas to flow through the valve without taking it apart.
Both methods achieve the same result. One requires special tools, one does not. One you can do without spending money, one you can't. If you're upset that people don't need your service, you should make yourself more indispensable.
